Technical Field
The present disclosure relates to a memory device, a host device, and a memory system including the same.
Related Art
Among memory systems including a host device and a memory device connected thereto, memory systems with improved security by encrypting commands and data transmitted/received between the two devices are in actual use.
Cryptosystems currently in use are perceived to be computationally secure against cryptanalysis. Actually implementing a cryptographic module in a memory system, however, may result in leaks caused by, for example, power consumption and processing time. Threats of side channel attacks are increasing, in an attempt to illicitly obtain secret information such as secret keys by observing these operational conditions by various physical means.
Examples of side channel attacks include power analysis attacks which are conducted to analyze secret information by studying the power consumption of a device. There is a report that Differential Power Analysis (DPA), which is an analysis of power consumption measurements by statistical functions, is one of the most powerful attacks among such side channel attacks (see Paul Kocher et al., “Introduction to Differential Power Analysis and related Attacks,” [online] Cryptography Research, searched in the Internet on Jul. 1, 2015, www.cryptography.com/public/pdf/DPATechInfo.pdf).
Various circuits are proposed as a countermeasure against the DPA attack. For example, Daisuke Suzuki et al. “Random Switching Logic: A Countermeasure against DPA based on Transition Probability,” [online], International Association for Cryptologic Research, searched in the Internet on Jul. 1, 2015, eprint.iacr.org/2004/346.pdf propose Random Switching Logic (RSL) circuit and Wave Dynamic Differential Logic (WDDL) circuit. The RSL circuit switches an operational mode of a logic circuit with a random number, so as to eliminate a biased state transition probability, thereby randomizing power consumption to prevent estimation of a cryptographic key. The WDDL circuit reduces a difference in current consumption due to difference in bit values in an arithmetic operation with a complementary circuit after precharging, so as to render the power consumption uniform.